Engine starter



' Nov 12, 1940. w, Fm GERALD 2,221,024

ENGINE STARTER Filed March 30, 1940 Lib/727 191F772 EPr'a/d tents 12,

ENGINE STARTER John w. Flt! Gerald, Milwaukee, Wis, assignor to Briggs &Stratton Corporation, Milwaukee, Win, a corporation of DelawareApplication March so, 194a, Serial No. 327,053.v

This invention relates to improvements in engine starters.

Engine starters now in use may be divided into two classes or types, theautomatic and the a manual. In the automatic type, the starter pinion isautomatically propelled into mesh with the engine ring gear andautomatically retracted upon starting of the engine; whereas,'in themanual type, the pinion is moved into mesh with the in engine rinla,gear either through a manually actuated system of levers or by anelectromagnet.

Obviously, therefore, the latter type of engine starter is by far themore complicated and costly. However, notwithstanding the additionalcost and complexity oi the manual type. the majority of present dayautomobiles use this type of engine starter. This follows from the factthat the engines are hard starting.

With the automatic type of starter, the pinion is thrown out of meshwith the ring gear at the first impulse or explosion of the engine. Ifthe engine fails to start, the pinion must be re-engaged with the ringgear to again crank the engine; but such re-engagement cannot beeffected until after the starting motor armature has come to rest.

The necessity for waiting ,between cranking cycles and the need forrepeating the process several times is sumcient inconvenience todissuade the use of the automatic type of starter except where theengine starts easily.

Another advantage of the manual type of starter over the automatic typeis that excessive current drain is avoided. As is well known, thebreakaway load which is applied each time the starter operates takesconsiderably more current than is required to keep the engine turningover in a continuous cranking operation. Hence, by obviating successiveand separate starts, the'manual type imposes less load on the battery.

With the manual type of starter, the starting pedal is depressed andheld down until the engine starts, for with this type of starter thepinion is moved manually into mesh with the ring gear and can be held inmesh as long as desired. When the engine starts, an overrunning clutchin the connection between the starter shaft and pinion permits thepinion to spin freely.

However, as often happens, this overrunning sequence, the starterarmature is spun by the engine at very high speeds. Spinning thearmsture shaft in this way loosens the armature windings and very oftenthrows them out radially and ruins the entire motor.

clutch does not function properly and as a conl Thus, it is evident thatalthough the manual type of starter can be held in engagement until theengine starts and in. this respectis advantageone over the automatictypeof starter, it does have objections in addition to itshigher costand 6 greater complexity.

It is, therefore, an object of this invention to provide an enginestarter which combines the advantages of the two presently known typesof starters to enableholding the starter in mesh 10 until the enginestarts without the possibility of subjecting the armature shaft todangerously high speeds.

More specifically, it is an object of this invention to provide anengine starter wherein the i5 starter pinion is held in mesh with theengine ring' gear until the pinion reaches a predetermined speed ofrotation, at which time it is released for automatic retraction.

With the above and other objects in view, which will appear as thedescription proceeds, this invention resides in the novel construction,comblnation and arrangement of parts substantially as hereinafterdescribed, and more particularly defined by the appended claims, itbeing under-' stood that such changes in the precise embo'die ment ofthe herein disclosed invention may be made as come within the scope ofthe claims.

The accompanying drawing illustrates onecomplete example of the physicalembodiment of the invention, constructed in accordance with the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a view in side elevation of an engine starter constructionin accordance with this invention, parts thereof being broken away andshown in section; a

Figure 2 is a cross sectional view taken through t Figure l on the planeof the line 22;

Figure 3 is a view similar to Figure '2 showing the parts arranged. tohold the pinion in mesh;

Figure 4 is a view similar to Figures 2 and 3, with the parts shown inthe positions they occupy at the time the pinion is freed forretraction; and

Figure 5 is a perspective view of the latchelements used to hold thepinion in mesh with the I ring gear.

Referring now particularly to the accompanying drawing, in which likenumerals indicate like parts, the numeral 5 designates the ringgear ofan engine with which the starter of this invention,

lit

motor and on which the starter mechanism is V mounted as a unit.

ally and axially resilient coupling H of the type forming the subjectmatter of theJohn W. Fitz Gerald Reissue Patent No. 20,686, issued April5, 1938, for Engine starter.

A screw threaded connection exists between the actuating or operatingmember ID and the pinion, which in the present instance consists of anexternally threaded extension I! on the operating member and aninternally threaded sleeve it to whichthe pinion is fixed.

The direction of screw pitch with relation to the direction of rotationis such that when the starting motor I is connected with the battery,the pinion l is automatically propelled forwardly into mesh with thering gear 5. This position is defined by a stop It against which thepinion abuts.

when the engine starts and causes the pinion to travel at a speed inexcess of that of the starter shaft, the screw threads function toretract 'the pinion out of mesh with the ring gear.

As pointed out hereinbefore, this type of starter is ideal fromthestandpoint of simplicity and low cost; but because the pinion isthrown out of mesh with the ring gear substantially immediately upon theinitial explosion of the engine,

it has proved disadvantageous for use with the engines that do not startreadily.

. To overcome this disadvantage without sacrificing any of the desirablefeatures of the automatic type of starter, the present inventionprovides speed controlled means for holding the starter .pinion 'inuntil the engine is fully started. This means consists of cooperatinglatch'parts or abutments l and it carried by the pinion operating memberl0 and the pinion sleeve l3, respectively.

- These latch parts or abutments are so positioned with relation to eachother that when the I pinion is propelled forwardly into mesh with thering gear, the latch parts or abutments engage,

asshownin Figure 3, to prevent retrograde rotation of the pinion andthus preclude retraction of the pinion as long as the latch parts areengaged and effect a direct torque transmitting connection from thepinion sleeve to the flange One of the cooperating latch parts yields orcame out of the way during engagement; and to facilitate this cammingaction, the two abutments have their approaching faces beveled orinclined, as illustrated.

' In the specific embodiment of the invention illustrated, the latchpart or abutment i6 is rigidly fixed to the pinion sleeve. l3 and theother being movable; and

enemas yieldingly maintains the abutment It in the path of the abutmentl6. This spring is anchored to the inner end of the arm it by a screwill and has its outer end bifurcated to form two spring fingers 22 whichpress the block I! against the arm ll. Hence, as the pinion moves outinto mesh with the ring gear, the abutments or latch partsareoperatively engaged.

When the starter revolves, centrifugal force acting on the block ll andthe latch part It tends to throw the same outwardly against the tensionof the spring fingers 22. At cranking speed, the centrifugal force iswholly inadequate to move the latch part it out of its operativeposition so that the starter can be held in" as long as necessary toeffect complete starting of the engine.

When the engine begins to operate under its own power and drives thestarter pinion at a speed substantially in excess of cranking speed, thecentrifugal force overbalances the spring tension and moves the latchpart it out of engagement with the latch part It to free the pinion forretraction.

The speed at which centrifugal force overbalances the spring tension maybe determined by varying the tension of the spring in any suitablemanner, as by an adjusting screw 28 threaded into the am It and bearingdown on the arched medial portion of the spring. In this manner,retraction of the pinion may be controlled to occur at any predeterminedspeed between cranking speed and safe armature speed.

The normal cranking speed of an engine is approximately 100 R. P. 101.;and since the gear ratio between the starter and engine is generally tento one, the starter motor armature turns over at approximately 1000 R.P. M. during cranking of the engine. No danger of damaging the armatureexists at speeds of 10,000 R. P. M. and even 12,000 E. P. M. Hence,there is a relatively wide range within which the speed responsive meansmay be set to function and release the pinions for retraction.

From the foregoing description taken in connection with the accompanyingdrawing, it will be readily apparent to those skilled in the art thatthis invention provides an engine starter which incorporates theadvantages of both the automatic and the manual type of star-ten What Iclaim as my invention is:

1. An engine starter of the type having a motor and wherein the pinionis automatically projected into mesh with an engine gear and isautomatically demeshed upon starting of the engine:

the combination of a smooth shaft adapted to be driven by the startingmotor; an externally threaded screw freely slidable and rotatable onsaid shaft; an outwardly extended annular flange on said screw; aresilient driving connection be-.

tween the shaft and the screw including a rubber-like collar encirclingthe shaft and frictionally engaging said flange; a pinion movablelongitudinally and rotatably with respect to said smooth shaft; aninternally threaded sleeve on the pinion threaded on the screw so that aspeed differential between the screw and pinion propels the pinionlongitudinally; cooperating abutments on the flange and the sleeveengageable upon projection of the pinion into mesh with the engine gearto effect a direct torque transmitting connection from the pinion sleeveto said flange which prevents premature retraction of the pinion fromthe engine gear, one of said abtuments centrifugally responsive meanscarried by the flange and operable to displace the movable abutment andfree the pinion for retraction upon the attainment of a predeflange onsaid screw; a resilient driving connection between the shaft and thescrew including a rubber-like collar encircling the shaft andfrictionally engaging said flange; a pinion movable longitudinally androtatably with respect to said smooth shaft; an internally threadedsleeve on the pinion threaded on the screw so that a speed differentialbetween the screw and pinion propels the pinion longitudinally; an armfixed to said annular flange and projecting therefrom to overlie theinternally threaded pinion sleeve; cooperating abutments on said arm andinternally threaded pinion sleeve providing a latch engageable uponprojection of the pinion to its operative position to establish a directtorque transmitting connection between the pinion sleeve and flange toprevent relative rotation between the pinion and the screw in thedirection effecting retraction of the pinion; and centrifugallyresponsive means mounted on the arm and operable to disengage said latchand release the pinion for retraction upon the attainment of apredetermined speed of rotation onthe part of the screw.

3.Inanenginestarterofthetypehavinga motor and wherein the pinion isautomatically projected into mesh with an engine gear and isautomatically demeshed upon starting of the engine: the combination of asmooth shaft adapted. to be driven by the starting motor; an externallythreaded screw freely slidable and rotatable on said shaft; an outwardlyextended annular flange on said screw; a resilient driving connectionbetween the shaft and the screw including a rubber-like collarencircling the shaft and frictionaiiyengaging said flange; a pinionmovable longitudinally and rotatably with respect to said smooth shaft;an internally threaded sleeve on the pinion threaded on the screw sothat's speed differential between the screw and pinion propels thepinion longitudinally; an arm on said flange projecting axially towardthe pinion said arm being of such length as to at all times overlie thepinion sleeve; a centrifugally responsive weight guided for movement onsaid arm; a leaf spring connecting the weight with said arm and andarranged to oppose movement of the weight in response-to centrifugalforce; and cooperating radially disposed abutments on the weight andpinion sleeve providing a latch engageable to effect a direct torquetransmitting connection between the pinion sleeve and said flange whichprevents premature retraction of thepinion, said weight and spring beingso coordinated that the centrifugal force developed at a predeterminedspeed of rotation of the sleeve releases the latch to free the pinionfor retraction.

JOHN W. FITZ GERALD. 851

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